Armored Cave Spider are the largest form of spiders found in Guild Wars. They are not particularly dangerous, especially compared to other creatures found in the Fissure of Woe, but their habit of hiding in trees, on cave ceilings, or below the ground can make for some nasty surprises.
It is a good practice to have members of your party (especially the casters in the back) attack all spiders in a group. This will disrupt Healing Spring and make them die much faster.
As soon as a player is in melee range, they will stop using Healing Spring altogether.
In the Spider Cave, the Armored Cave Spiders appear in a set pattern. When a Doubter's Dryder is aggroed, it will spawn two groups of spiders (each has 3 spiders). One group will spawn immediately in front of the dryder and the other will spawn behind the dryder a few moments later. It is important to be mindful of this back group and make sure your tanks are meeting them first, otherwise, they will spread their poison and interrupts on your casters.
If you put a condition on a spider, it will use Healing Spring right after using Melandru's Resilience. This is a good way for solo farmers to time their healing skills.
They will only use Savage Shot when their target is at low health, unless you're using a spell.